The present invention relates to parts for car body comprising plastic-covered metallic material obtained by sticking a plastic film having a topcoat finishing property on a molded and electrodeposition coated metallic material and to a coat-finishing process of a car body using said parts for car body for at least a part of the shell body of the car body.
In car bodies of passenger cars and light cars, a part to which equipments such as an engine and a chassis are not installed and which is composed mainly of sheet metal is called “a shell body” and is composed usually of “a main body” composed of an underbody, a side member, a roof, a cowl an upper back and a lower back and “an outer covered part” such as a hood, a front balance, a front fender, a cowl louver, doors and a luggage (back doors).
These main body and outer covered part have so far been formed by cutting, molding and assembling metal plates into sizes and shapes of the respective constitutional parts, immersing them in a cationic electrodeposition paint bath to coat the front sides, back sides and end faces thereof to form primer coat paint films and then applying an intermediate coat paint and a top coat paint on the outside parts.
In recent years, however, step saving, energy saving, a reduction in CO2 and VOC and environmental protection in a coating line are strongly desired in coating car bodies. In addition thereto, a chipping resistance and a corrosion resistance of a combined paint film are requested to be further improved. In order to elevate this chipping resistance, it is proposed to provide a barrier coat for forming a visco-elastic paint film in a layer between these paint films, but there are the defects that a coating step is added and the production cost goes up.